New satellite images of a North Korean rocket site show evidence of increased preparation for a space launch that Washington sees as cover for a long-range missile test.

The U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies said Sunday that satellite photos taken last Wednesday show a mobile radar trailer, not previously present at the new Tongchang-ri site, and rows of what appear to be empty fuel and oxidizer tanks.

The Institute said the photos also show what appears to be activity near the launcher assembly building, where news reports indicate the stages of the Unha-3 rocket are located.

Pyongyang says the launch will put a functional satellite into orbit as part of the celebration of the 100th birthday of the late leader Kim Il Sung, the founder of the communist state and Kim Jong Un's grandfather.

The United States, Russia, South Korea and Japan all have condemned the planned launch. Even Pyongyang's long-time ally, China, has expressed rare disapproval, while U.N. Secretary-General Ban Ki-moon said he was "deeply concerned."

The Aspen Institute "think tank" in Berlin said Sunday that North Korean and American delegations had held informal talks in Germany. Charles King Mallory, executive director of the Institute, confirmed the meeting but did not comment in detail on the contents of the so-called "track two" talks or who participated in them.

"Yes there was a meeting," admitted Mallory, "it discussed the four principle areas of the September 15th 2009 joint statement, those would be: peace treaty, they would be economic cooperation and development, denuclearization and confidence building measures, that's what happened."

The North's official Korean Central News Agency said Monday that Pyongyang will hold a special Workers' Party conference on April 11, just days before the satellite launch. Analysts say the delegates are likely to appoint the country's new leader, Kim Jong Un, to the post of party general-secretary, previously held by his father Kim Jong Il, who died in December.

The North's announcement of the launch plan came just over two weeks after Pyongyang reached a deal with the United States to suspend operations at its Yongbyon uranium enrichment plant and impose a moratorium on long-range missile tests and nuclear tests in return for 240,000 tons of food aid.

Washington said last week it is suspending plans to start food deliveries as it can no longer trust the North to stick to arrangements on monitoring distribution.

Pyongyang criticized the U.S. move Saturday as an "over-reaction" that would kill the February 29 agreement.

Japan is inreasingly concerned at the situation there, and urges the DPRK to stop the tests and explain their situation openly and freely with the international community, particularly with Japan, China, South Korea, Russia and the US, for the sake of stability and its people.

The Republic of Korea reiterates our often publicised position: the DPRK are not a country to be negotiated with, they should be treated with the utmost caution. These missile test confirm global suspicions that they are harbouring a significant weapons arsenal. Consequently, ther DPRK need to be subject to embargos in an attempt to bring peace to our region.